Compressed air assisted fuel injection system

ABSTRACT

An internal combustion engine having a compressed air assisted fuel injection system. The injection system has a compressed air accumulator with a first aperture into the cylinder of the engine and a second aperture into the crankcase of the engine. The two apertures are located at opposite ends of the accumulator and the accumulator has a tube shape. The accumulator blows off pressure every time one of the ports into the cylinder is closed. The tube shape of the accumulator forms a tuned reflection pipe for a compression wave from the cylinder to generate a reflected compression wave for assisting in delivering fuel and air into the cylinder. The two apertures are adapted to be opened and closed by the piston head of the engine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fuel injection systems for internalcombustion engines and, more specifically, to a control system for atwo-stroke engine.

2. Prior Art

Several alternatives for the pressurized air utilized in the injectionare known; a separate air pump may be utilized, the air source may bederived from the cylinder of the engine during the compression or theexpansion stroke, or the air may be derived from the crankcase pumpingof the engine. In low cost applications it is desired to utilize the airsource from the crankcase or the cylinder, so as to avoid the added costand complexity of the separate air pump. In the application of pneumaticinjection to larger cylinder sized engines, in general larger than 50 ccdisplacement, it is generally desirable to utilize injection pressurederived from the cylinder pressure because a high gas pressure may beobtained for injection. In smaller engines this tapping utilizes adisproportionate quantity of the cylinder charge gases and, thus,adversely affects the performance of the engine. It is therefore morepractical to utilize the crankcase pumping source in such cases.

It is most beneficial to inject the fuel into the cylinder near to orslightly after the bottom dead center position of the piston. Thisinjection timing avoids introducing the fuel into the early phase of thecylinder scavenging, and thus avoiding short circuit loss to theexhaust. Further, the fuel is introduced into the cylinder when thepressure in the cylinder in near atmospheric pressure, allowing the bestuse of the limited injection pressure to spray and therefore atomize thefuel charge. Thus, it is desirable to have a pneumatic injection timingnear to the bottom dead center timing of the piston and that this timingbe relatively constant with changing engine operational parameters suchas speed and throttle position or load.

Several methods for operating an injection valve are taught in the priorart. U.S. Pat. No. 4,693,224 teaches the use of an electronic solenoidto operate the injection valve. This is generally unacceptable forapplication to small high speed engines because of the necessity of anengine control unit to operate the valve and the relatively high powerrequirement to drive the high speed solenoid, both adding prohibitivecosts to the engine. The most common method of operating the valve astaught by the prior art is the use of some form of kinematic valvelinkage driven from the crank shaft of the engine. These valves take theform of oscillating valves driven by cams as taught by a system called“PRO-JECT” described in an article “Pro-Ject Air-Assisted Fuel InjectionSystem For Two-Stroke Engines”, SAE 940397 from Universita di Pisa and asystem from L'Institut Francais du Petrole described in an article “ANew Two-Stroke Engine With Compressed Air Assisted Fuel Injection ForHigh Efficiency Low Emissions Applications” by Duret et al. in SAE880176, or rotating type valves as taught by Honda in an article “AnExperimental Study of Stratified Scavenging Activated Radical CombustionEngine” by Ishibashi, SAE 972077. A problem exists with all the forms ofkinematically driven valves in that they need precision surfaces andhigh quality materials for both the sealing members of the valve and therunning portions of the drive. Valves mounted such that they are exposedto combustion gases must also be fashioned from expensive heat resistantmaterials. Additionally, many parts require lubrication which is notpresently available in the simple two-stroke engine. Thus, themechanical type valve arrangements add significant costs and complexityto the construction of the engine. Therefore, it is desirable to fashionan injection control valve that may be made of inexpensive materials andneed not be manufactured to high tolerance, the valve and drivemechanism most preferably would require no high temperature capabilityor additional lubrication.

Further, an additional problem is commonly known to exist in theapplication of oscillating valves to high speed engines. The problem isthat of the greatly increasing drive force required as the engine speedincreases. For a fixed valve opening amplitude or lift, the accelerationrequired of the valve increases in proportion to the square of the valveopening frequency and therefore the engine speed. Further, the forcerequired to drive the valve increases in proportion to the acceleration.Thus, the force required to drive the valve increases in proportion tothe square of the engine speed. For single acting valve trains, that isvalves actively driven in only one direction, these high drive forceslead to the use of large return springs to over come the valve inertialforces and prevent valve float, and consequently even more elevateddrive forces. It is desirable to drive the valve in both directions,both open and closed, to avoid the use of large spring members and theassociated high forces, while still attaining high speed operation.Mechanical means can be applied to drive the valve in both directions,however, this requires an even higher degree of precision and leads toeven greater cost and complexity of the engine.

The final method of driving the injection valve is to operate the valvepneumatically. Pneumatic operation is affected by driving a pistonthrough the use of a differential gas pressure across the two opposingfaces of the piston. This piston in turn drives the valve. The use ofpneumatic operation is common practice in gas flow control, in suchdevices as flow regulators and flow control valves such as spool valves.In engine operation pneumatically controlled valves are commonlyutilized in carburetor operation for flow control, regulation ofpressures and various operations such as driving liquid injections andopening addition flow paths. Examples of such use are shown in U.S. Pat.Nos. 5,377,637; 5,353,754; 5,197,417; 5,197,418; 4,846,119 and4,813,391. In their application to engines where limited motion isrequired the piston is often in the form of a diaphragm, acting as thepiston seal, and diaphragm plates functioning as the drive piston.

The use of pneumatic valve operation for control of a pneumaticinjection system is taught in WO 96/07817 and EP 0789138A1. Thesesystems utilize an injection valve placed in the head of the combustionchamber and operated on by pressures derived from various locations ofthe engine to influence the valve motion.

IAPAC direct fuel injection systems which use a cam to controlintroduction of scavenged compressed air from a crankcase have been usedin the past to reduce pollutant emissions and fuel consumption intwo-stroke engines. European Patent Office patent publication No. EP0789138 discloses a camless IAPAC system (now known as SCIP) which usesa diaphragm connected to a valve, a spring, pressure from the enginecrankcase, and pressure from combustion expansion gases in thecombustion chamber to delay movement of the valve.

A problem exists with the cam driven IAPAC system in that addedcomponents increase cost to the engine. A problem exists with the SCIPsystem in that misfires in the combustion chamber result in nocombustion expansion gases to delay movement of the valve. Misfires in atwo-stroke engine can happen as often as one out of every three pistoncycles. Thus, injection of fuel and air into the combustion chamberusing a SCIP system can result in a substantial number of prematureinjections; about one-third of the time.

WO 96/07817 teaches a pneumatic valve that is opened when the injectionpressure as derived from the crankcase of the engine overcomes thepressure from the valve closing spring and a delayed pressure wavederived from the crankcase. A problem exists in such a system that theinjection pressure as derived from the crankcase is highly dependent onthe engine operating condition. The peak pressure attained by thecrankcase in a small two stroke engine varies with the throttleposition. At wide open throttle (WOT) the peak pressure may reach 6 to 7pounds per square inch above atmospheric pressure (psig), while at lowthrottle opening the peak pressure only reaches 1.5 to 2 psig. Thus theinjection pressure available to open the valve is highly dependent onoperating condition and thus, the injection timing is dependent onoperating conditions. Further, in a small high speed engine the area ofthe valve is severely limited by the available space in the engine. Thissmall area and the relatively low injection pressure available to act onthat area lead to a small available force for valve opening. Thiscoupled with the previously mention phenomenon of the required highforce at high speed severely limit the use in the small high speedapplication. Thus it is desirable to have a valve actuation system thatis largely independent of injection pressure, further it is desired thatthe primary motive force be derived from the diaphragm or drive pistonsuch that the valve operation is largely independent of valve area.

A further problem exists with WO 96/07817. The wave used to control theinjection is derived from the crankcase pressure through a long ‘delay’line. The delay line is used to control the time of arrival of thepressure wave at the valve. The Transit time in seconds of the pressurewave is fairly constant, however the transit and arrival timing in termsof crankshaft position, and therefore piston position, is highlydependent on engine speed. Thus, the injection timing is highlydependent on engine speed. Further the delay line also acts to attenuatethe pressure wave, this attenuation is more acute with increasing enginespeed. The attenuation coupled with the relatively weak crankcase waverender an inadequate control pressure in high speed/high load operation.It is desired to fashion a valve control system that is largelyindependent of engine speed.

Other embodiments of the art teach the use of controlling crank ‘cheeks’and additional delay lines to further control the pressure waves. Thesecontrolling cheeks must be made as precision valve surfaces to controlthe small flows associated with the valve control and thus addsignificant cost to the engine. The additional delay lines impartfurther speed dependence on the injection timing.

These deficiencies in WO 96/07817 are also pointed out in EP 0789138A1.EP 0789139A1 teaches the use of a valve as in the previous patent wherethe wave utilized to delay the injection is derived from the cylinderexpansion gases. The expansion wave is again delivered to the valvecontrol diaphragm through a delay line. In some embodiments the openingforce available is enhanced by the use of longer delay lines from eitherthe cylinder expansion gases or the crankcase wave and is delivered tothe opposite side of the actuating diaphragm. Although this embodimentdoes enhance the opening force and improve on the problem of lowpressure of the crankcase wave, the deficiency of the injection timingbeing highly dependent on engine speed is further introduced. Thus theinjection behavior may only be optimized for a specific engine speed.

A further and critical problem is introduced through the use of theexpansion gases to control the valve motion. Small two-stroke enginesmostly exhibit poor combustion characteristics with misfire or partialcombustion occurring every couple of strokes. During misfire there areno combustion expansion gases to be utilized to delay the injection.Further, due to ring seal leakage, the pressure during the normalexpansion stroke after misfire is often sub-atmospheric, thus furtheradvancing the injection timing. Therefore, as often as every thirdstroke the injection occurs at, or before, the beginning of the freshair scavenging of the cylinder, thereby short circuiting both theunburned charge from the misfired stroke and a large portion of theearly injected charge for the following stroke. It is thereforedesirable to fashion an injection control system that is largelyindependent of combustion expansion gases from combustion of anindividual piston cycle.

In both of the aforementioned publications the primary motive force forthe closure of the valve is a spring positioned in the diaphragmchamber. This spring must be of sufficiently low force to allow thevalve to be opened by the low injection pressures or diaphragm driveforces available. This low force combined with the increasing inertialforces of the valve at high speed lead to later and later valve closureand eventually valve float. Again it is desirable to fashion a doubleacting valve drive system that drives the valve both open and closed ina positive way.

A normal feature of small two-stroke engines is the lack of a separatelubrication system. The lubricant is commonly delivered to the crankcasecomponents and the piston-cylinder unit through being mixed with thefuel. In direct injected engines, including pneumatically injectedengine, of the prior art the fuel with no lubricant is delivered to thecombustion chamber. This requires the addition of a separate lubricationsupply pump and system for the crankcase and piston-cylinder unit, thusadding cost and complexity to the engine. It is therefore desirable tohave the injection system supply a limited but significant quantity offuel oil mixture to the crankcase to meet the engine lubricationrequirement with limited additional complexity or cost.

SAE Paper 941678 entitled “Delayed Charging: A Means to ImproveTwo-Stoke Engine Characteristics” by Rochelle and SAE Paper 951784entitled “Emission and Fuel Consumption Reduction in a Two-stroke EngineUsing Delayed-Charging” by Rochelle, disclose use of an attemptedconstant flow pressure, by use of a surge tank, but this promotesleaking of fuel between the piston and the cylinder that can increasehydrocardon emissions. Rochelle also has a physically open path betweenthe crankcase and the combustion chamber throught the surge tank at onepoint which the present invention avoids. Rochelle also neglectsacoustic effects.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, an internalcombustion engine is provided having a crankcase, a cylinder connectedto the crankcase, and a compressed air assisted fuel injection systemconnected between the crankcase and the cylinder. A reciprocating pistonhead is located in the cylinder. The compressed air assisted fuelinjection system has a conduit system with a first aperture into thecylinder forming a fuel and compressed air injection port and a secondaperture into the crankcase forming a compressed air entrance and blowoff port. The piston head opens and closes the two ports as the pistonhead reciprocates in the cylinder. The first and second apertures arespaced relative to each other and the piston is sized and shaped suchthat the piston head substantially simultaneously opens the compressedair entrance and blow off port and closes the fuel and compressed airinjection port and wherein the blow off port remains open as the pistonhead moves to and through the top dead center position.

In accordance with another embodiment of the present invention aninternal combustion engine is provided having a compressed air assistedfuel injection system connected between a source of compressed air and acylinder of the engine. The injection system has a compressed airaccumulator and means for relieving compressed air pressure in theaccumulator during a majority of when a fuel and compressed airinjection port of the injection system is closed by a piston head of theengine and the piston head is moving towards a top dead center position.

In accordance with another embodiment of the present invention, aninternal combustion engine is provided having a compressed air assistedfuel injection system connected between a source of compressed air and acylinder of the engine. The injection system includes an accumulator forproviding a charge of compressed air and an aperture from theaccumulator into the cylinder. The aperture is sized to restrict flow ofthe charge into the cylinder such that the entire charge is pressurizedduring an entire fuel and compressed air injection period of the engine.

In accordance with another embodiment of the present invention, aninternal combustion engine is provided having a compressed air assistedfuel injection system connected between a source of compressed air and acylinder of the engine. The injection system has a conduit between thesource of compressed air and the cylinder. The conduit has a firstaperture into the cylinder and a second aperture. The engine has meansfor opening and closing the first and second apertures. The secondaperture is closed while the first aperture is open and the secondaperture open during a majority of when the first aperture is closed.

In accordance with another embodiment of the present invention, aninternal combustion engine is provided having a compressed air assistedfuel injection system connected between a crankcase and a cylinder ofthe engine. The injection system has a conduit between the crankcase andthe cylinder. The injection system also has a fuel metering device witha fuel exit into the conduit. A piston head of the engine opens andclosed access to the conduit from the cylinder and the crankcase. Accessbetween the cylinder and the conduit is closed and access between thecrankcase and the conduit is open during vacuum pressure in thecrankcase such that fuel is vacuum pulled into the conduit during aforward stroke of the piston head and air is compressed into the conduitduring a rearward stroke of the piston head.

In accordance with another embodiment of the present invention, aninternal combustion engine is provided having a compressed air assistedfuel injection system connected between a source of compressed air and acylinder of the engine. The injection system has an accumulator conduitwith an injection port into the cylinder. The accumulator conduit has alength and shape to form a tuned reflection pipe to reflect acompression wave, which enters the injection port from opening of theinjection port after combustion in the cylinder, and to deliver thereflected compression wave to the injection port at a predeterminedperiod to assist in delivering fuel out of the injection port and intothe cylinder.

In accordance with another embodiment of the present invention, aninternal combustion engine compressed air assisted fuel injection systemis provided having an accumulator conduit with two apertures located ata cylinder and a crankcase of the engine, respectively, the accumulatorconduit has a predetermined length and the apertures are selectivelyclosable such that a compression wave from combustion in the cylinderentering the conduit at a first one of the apertures travels through theconduit and is reflected back to the first aperture wherein the conduitforms a tuned reflection pipe for the first aperture such that thereflected compression wave assists in delivering fuel out of the firstaperture into the cylinder.

In accordance with one method of the present invention, a method ofinjecting air and fuel into a cylinder of an internal combustion engineis provided comprising steps of compressing air into an accumulator;opening an injection port into the cylinder and injecting the compressedair from the accumulator and fuel from the injection port into thecylinder; closing the injection port; and opening a blow off port of theaccumulator to relieve residual compressed air pressure from theaccumulator.

In accordance with another method of the present invention, a method ofmanufacturing an internal combustion engine is provided comprising stepsof providing a cylinder with an injection port; and connecting acompressed air assisted fuel injection system to the cylinder. Theinjection system has a fuel metering device and a compressed airaccumulator. The compressed air accumulator is provided with a lengthand shape to reflect a compression wave received at the injection portback to the injection port after a piston head of the engine moves pasta bottom dead center position.

In accordance with another method of the present invention, a method ofdelivering air from a compressed air assisted fuel injection system intoa cylinder of an internal combustion engine is provided comprising stepsof compressing air into an accumulator of the injection system;releasing a first amount of compressed air out the accumulator andthrough an injection port into the cylinder at a first pressure; andreleasing a subsequent second amount of compressed air out theaccumulator and through the injection port into the cylinder at a secondpressure higher than the first pressure.

In accordance with another method of the present invention, a method ofdelivering fuel and air from a compressed air assisted fuel injectionsystem into a cylinder of an internal combustion engine is providedcomprising steps of providing the injection system with a compressed airaccumulator having a channel between a crankcase of the engine and thecylinder; delivering a first amount of fuel and compressed air from thechannel into the cylinder; and delivering a subsequent second amount offuel and compressed air at a higher rate from the channel into thecylinder, wherein the step of delivering the first and second amountsoccur in a single injection cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present invention areexplained in the following description, taken in connection with theaccompanying drawings, wherein:

FIGS. 1A-1E are partial schematic diagrams of an engine incorporatingfeatures of the present invention with the piston head at variousdifferent operational positions;

FIG. 2 is a diagram illustrating open and closed positions of the twoapertures of the accumulator based upon crankcase rotation and resultingpiston head positioning;

FIG. 3 is a graph of pressures in the crankcase, combustion chamber andaccumulator relative to piston head positioning in the cylinder;

FIG. 4A-4D are schematic diagrams similar to FIG. 1A for pistonlocations between 1B and 1C of FIG. 2 and showing compression wave andreflected compression wave movement;

FIGS. 5A-5C are pressure diagrams of for three points along the lengthof the accumulator conduit;

FIG. 6 is a graph as in FIG. 3 when a misfire occurs;

FIG. 7 is a diagram as in FIG. 2 of an alternate embodiment of theengine;

FIG. 8 is a partial schematic diagram similar to FIG. 1D of an alternateembodiment with a cross-sectional view of the piston head;

FIG. 9 is a partial schematic diagram of an engine with an alternateembodiment of the accumulator; and

FIG. 10 is a partial schematic diagram of an engine with anotheralternate embodiment of the accumulator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1A, there is shown a schematic view of an internalcombustion engine 10 incorporating features of the present invention.Although the present invention will be described with reference to theembodiments shown in the drawings, it should be understood that thepresent invention can be embodied in many alternate forms ofembodiments. In addition, any suitable size, shape or type of elementsor materials could be used.

The engine 10 is a two-stroke engine having a cylinder 12, a piston 14,a crankshaft 16, a crankcase 18, and a fuel injection system 22 having afuel metering system 20. The present invention relates to the control ofa low pressure injection in an internal combustion engine. A particularfield of application of the invention is a two-stroke internalcombustion engine. The specific application described is to a small highspeed two-stroke engine, such as utilized in handheld power equipmentsuch as leaf blowers, string trimmers and hedge trimmers, also inwheeled vehicle applications such as mopeds, motorcycles and scootersand in small outboard boat engines. The small two-stroke engine has manydesirable characteristics, that lend themselves to the aboveapplications, including: simplicity of construction, low cost ofmanufacturing, high power-to-weight ratios, high speed operationalcapability and, in many parts of the world, ease of maintenance withsimple facilities.

The prominent drawback of the simple two-stroke engine is the loss of aportion of the fresh unburned fuel charge from the cylinder during thescavenging process. This leads to poor fuel economy and, mostimportantly, high emission of unburned hydrocarbon, thus rendering thesimple two-stroke engine incapable of compliance with increasinglystringent governmental pollution restrictions. This drawback can berelieved by separating the scavenging of the cylinder, with fresh air,from the charging of the cylinder, with fuel. This separation can beachieved by injecting the liquid fuel into the cylinder or morepreferably by injecting the fuel charge by utilizing a pressurized airsource, separate from the fresh air scavenge, to spray the fuel into thecylinder. In a preferred embodiment of the present invention, thedisplacement size of the engine is about 16 cc to about 100 cc, butcould be larger or smaller. These sizes of engines are used for suchthings as string trimmers, chain saws, leaf blowers, and other hand heldpower tools. The engine could also be used on a tool such as a lawnmower, snow blower or motor boat outboard engine. The cylinder 12 has aspark plug (not shown) connected to its top, a bottom which is connectedto the crankcase 18, an air inlet 24, a combustion chamber 26, anexhaust outlet 28, and an injection port or inlet 30 into the combustionchamber. The fuel metering system 20 could be any suitable type ofsystem, such as a carburetor or electronic fuel injector. However, anadvantage of the present system is that there is no need for highprecision timing or spray quality for the fuel metering system. Arelatively simple metering system that delivers drops of fuel could beused. In the embodiment shown in FIG. 1A the injection port 30 is anopen type of port; i.e.: with no flow check valve into the combustionchamber 26. However, an alternate embodiment could be provided which hasa flow check valve at its injection port, such as disclosed in U.S.patent application Ser. No. 09/065,374 which is hereby incorporated byreference in its entirety. However, any suitable check valve could beused. The injection port 30 is located in a side wall of the cylinder 12and is shaped to input fuel and air in an upward direction towards thetop of the cylinder head. However, in alternate embodiments the inletcould be located in the top of the cylinder head or be shaped to directfuel towards the top of the piston 14.

The fuel injection system 22 is a compressed air assisted system. Theinjection system 22 comprises an accumulator 34. The accumulator 34, inthis embodiment, has an inlet 38 connectable to pressure inside thecrankcase 18 and an exit at the injection port 30. The accumulator 34functions as a collector and temporary storage area for compressed air.In this embodiment the source of the compressed air is air scavengedfrom the crankcase 18. The piston 14 compresses the air in the crankcase18 on the piston's downward stroke. In a preferred embodiment the twoapertures 30, 38 are both provided in the cylinder 12; one above the airinlet 24 and one below the air inlet. In the preferred embodiment bothapertures 30, 38 are piston ported. In other words, the piston. head 40is sized and shaped to open and close access through the apertures 30,38 as the piston head 40 reciprocates up and down in the cylinder 12.The accumulator 34, in this embodiment, is a simple channel between thetwo apertures 30, 38. However, in alternate embodiments more complicatedshapes could be provided as further understood from the descriptionbelow. The channel 34 could be partially machined into an exteriorsurface of the cylinder 12 with a cap then being attached to thecylinder to form and enclose the channel 34 with only the two apertures30, 38. However, the accumulator could be provided in a separate memberattached to the cylinder 12. In the preferred embodiment an exit fromthe fuel metering system 20 is located in the channel 34 proximate theinjection port 30.

As will be further described below, the fuel injection system 22 hasminimal moving parts; merely whatever moving parts are in the fuelmetering device 20. Otherwise, the fuel injection system 22 uses thepiston head 40 to open and close its ports 30, 38. Timing of the openingand closing of the ports 30, 38 will be dependent upon location of theports along the length of the cylinder 12. Referring to FIGS. 1A-1E and2 the operation of the injection system will now be described. FIG. 2 isintended to illustrate a line of events of opening and closing of theapertures 30, 38 during a single full piston cycle (which results from a360° rotation of the crankshaft 16) as a 360° chart corresponding topiston head location as based upon angular position of the crankshaft 16starting at the top dead center (TDC) position of the piston 14. Area Aindicates when the piston head 40 blocks the aperture 30. Area Bindicates when the piston head 40 blocks the aperture 38. At TDC theinlet 30 is blocked by the side of the piston head 40. At TDC theaperture 38 is open. The air inlet 24 is closed by the piston head atposition IC which is about 60° after top dead center (ATDC). FIG. 1Ashows the piston head 40 at about 90° ATDC as indicated by position 1Ain FIG. 2 moving downward in the cylinder 12 as shown by arrow C awayfrom the top dead center position of the piston head. The piston head 40is blocking the inlet 30, the exhaust outlet 28 and the air inlet 24,but the aperture 38 is open. With the piston head 40 moving towards thecrankcase 18, air from inside the crankcase 18 is pushed into theaccumulator 34 through the aperture 38 as indicated by arrow D.Referring also to FIG. 3, a graph of pressures during a single pistoncycle are shown relative to zero gage, pressure of one atmosphere. AtTDC the pressure E in the crankcase 18 and the pressure F in theaccumulator 34 at the inlet 30 are substantially the same. They remainsubstantially the same as the piston head moves through position 1A. Asthe piston head 40 continues to move down in the cylinder 12 the exhaustoutlet 28 is opened at E0. Pressure G in the combustion chamber 26,caused by expanding gases from combustion, starts to drop.

As the piston head 40 moves towards position 1B, illustrated in FIG. 1B,the aperture 30 is beginning to be opened, as the piston head 40uncovers the aperture 30, and the aperture 38 is beginning to be closed,as the piston head 40 starts to block the aperture 38. The piston headuncovers the inlet 30 at about 100° of rotation of the crankshaft afterTDC (ATDC). In this embodiment the piston head 40 completely closes theaperture 38 at about the same time the piston head opens access to thetransfer channel 42 (see FIG. 1C) at position TO when the transfer 42opens.

Referring also to FIGS. 4A-4D pressures and movement of gases in theaccumulator 34 during the period between 1B and 1C will be furtherdescribed. FIGS. 4A-4D schematically illustrate the accumulator 34 as aclosed end pipe. This is because the aperture 38 is effectively closedby the piston head 40 substantially entirely while the aperture 30 isopen. FIG. 4A generally corresponds to position 1B. In this position theaccumulator 34 has a volume 44 of compressed air, a volume 46 ofcompressed air and fuel, and the beginning of a slight buffer 48 ofcombustion gases. In addition, a compression wave 50 enters theaccumulator 34 from the aperture 30 and travels down the accumulator atthe speed of sound as illustrated by arrow H towards the now closedaperture 38 _(closed). Pressure F at the inlet 30, as seen in FIG. 3,spikes upward at 1B because of entry of combustion gases into the inlet30 and entry of the compression wave 50.

FIG. 4B corresponds to a short time later. The buffer 48 of combustiongases has further pushed into the inlet 30. The buffer 48 helps to heatthe inlet 30 and helps to prevent fuel in the accumulator from directlyshort circuiting to the exhaust outlet 28. The compression wave 50 hasmoved further down the accumulator 34. FIG. 4C corresponds to a shorttime after the transfer 42 has opened at point TO. As seen in FIG. 3,the pressure F at the inlet 30 is now higher than the pressure G in thecombustion chamber because of gases exiting the exhaust outlet 28.Therefore, the buffer 48 is pushed into the cylinder 12 (acting as adelay before entry of the air and fuel 46) and the air and fuel 46 startto enter the cylinder 12. The compression wave 50 has reflected off ofthe closed aperture 38 _(close) and, more specifically, reflected off ofthe side of the piston head 40 covering the aperture 38. Thus, thecompression wave 50 has become the reflected compression wave 50′. Thereflected compression wave 50′ is now traveling up the accumulator 34back towards the inlet 30 as indicated by arrow H′. FIG. 4D correspondsto about the position 1C when the piston head is at bottom dead center(BDC). This generally corresponds to the BDC position shown in FIG. 1C.The reflected compression wave 50′ arrives at the inlet 30 and exitsinto the cylinder 12. This causes a second spike in the pressure F atthe inlet 30 as seen on FIG. 3. This second spike of pressure helps topropel fuel and air into the cylinder 12 at an accelerated rate. Thecompression wave is essentially an acoustic wave. Thus, the wave travelsat the speed of sound. The timing of the delivery of the reflectedcompression wave back to the injection inlet 30 can be varied by varyingthe length of the accumulator conduit. A shorter accumulator conduitwill deliver the reflected wave sooner and a longer accumulator conduitwill deliver the reflected wave later. Thus, the length of theaccumulator conduit 34 can be selected to deliver the reflectedcompression wave back to the injection inlet 30 at any suitable time. Asshown in FIG. 3, there are three general groups of pressures of air andfuel F₁, F₂, F₃ exiting the inlet 30 into the cylinder and, thus, threecorresponding rates of flow during these three pressure periods. Hence,a first volume from the inlet 30 will enter the cylinder 12 at a firstrate, a subsequent second volume will enter the cylinder at a secondhigher rate, and a subsequent third volume will enter the cylinder at athird lower rate. However, in an alternate embodiment the accumulatorcan be configured to deliver the reflected compression wave closer tothe period 1D when the inlet 30 is about to be closed. Thus, only twodifferent rate periods need be provided. Alternatively, the accumulatorcould be configured to deliver more than one reflected compression waveback to the inlet 30, such as by providing the accumulator with multiplechannels or multiple reflection surfaces. In effect, by closing theaperture 38 and using the closed aperture as a reflection area, theaccumulator 34 functions as a tuned reflection pipe for the compressionwave 50.

Referring also to FIGS. 5A-5C, charts of pressure on a reference scaleat points 1, 2 and 3 in FIGS. 4A-4D are shown relative to time. Pressureat point 1 increases at time 4A corresponding to FIG. 4A when thecompression wave enters the inlet 30. The pressure at point 1 trails offat times 4B and 4C corresponding to FIGS. 4B and 4C, respectively. Thepressure at point 1 then sharply rises at time 4D corresponding to FIG.4D when the reflected compression wave reaches point 1 and subsequentlydecreases after time 4D. FIG. 5B shows how pressure at point 2 risesjust before time 4B as the compression wave 50 passes through point 2,goes down, then rises again just before time 4C as the reflectedcompression wave 50′ passes, and then the pressure goes down again. FIG.5C shows how point 3 merely has the one pressure spike from thecompression wave's impact and reflection off of the closed aperture 38_(close).

As the reflected compression wave 50′ exits the inlet 30 it causes thefuel and air in the cylinder 12 to be greatly disturbed; in effectfunctioning as a shock wave. This helps to atomize the fuel anddistribute the fuel better in the air. In addition, the reflectedcompression wave assists in removing fuel droplets that might beadhering to tips or edges of the inlet 30 by surface adhesion or surfacetension. The compression wave shocks the fuel off of the surface andinto the cylinder 12. The compressed air 44 continues to push out theinlet 30 until the inlet is closed by the piston head again as shown inFIG. 1D. The residual air in the accumulator 34 after the inlet 30 isclosed, just after 1D, is still pressurized. The inlet 30 completelycloses shortly before the exhaust outlet 28 is closed at EC. Theaperture 38 opens at substantially the same time the aperture 30 isclosed. However, in alternate embodiments opening of the aperture 38could be configured to occur before the aperture 30 is closed or,alternatively, after the aperture 30 is closed. The opening of theaperture 38 functions as a blow off port to relieve residual pressurefrom the compressed air in the accumulator 34 back into the crankcase 18as shown by arrow I in FIG. 1D. Relieving pressure from the accumulator34 when the inlet 30 is closed prevents an excessive amount of fuel frombeing pushed between the piston head 40 and the inside cylinder wallthat could otherwise raise hydrocarbon emissions.

With the piston head 40 rising as shown by arrow J in FIG. 1D towardsthe TDC position, crankcase pressure E drops below 1 atmosphere as seenin FIG. 3. Thus, when aperture 38 is opened, not only is pressure in theaccumulator 34 relieved, but a vacuum pressure is created in theaccumulator 34. This vacuum pressure is used to pull fuel from the fuelmetering device 20 and thus assist in delivering fuel into theaccumulator. As seen in FIG. 3, the pressure F in the accumulator 34 nowgenerally matches the pressure E in the crankcase 18 once again.Referring also to FIG. 1E the piston head 40 is shown at its TDCposition. The air inlet 24 was opened at point IO. In this embodimentthe inside wall of the cylinder 12 has a groove 60 between the inlet 30and the inlet 24. This provides a path for a small amount of fuel(containing lubricant) to pass through the groove 60 as indicated byarrow K and lubricate bearings in the piston and crankshaft. However,the groove need not be provided. In an alternate embodiment a hole couldbe provided between the inlet 24 and the inlet 30 which would be spacedfrom the inside wall of the cylinder to deliver lubricant behind thepiston head. The engine 10 could have an additional or alternativelubrication system.

As is known in the art for small two stroke engines, misfires (i.e.: nocombustion in the combustion chamber) can occur as much as one-third ofthe time. If a misfire occurs in the engine 10 a compression wave willnot pass into the accumulator 34. Referring to FIG. 6 a graph ofpressures E and F similar to FIG. 3 is shown when there is a misfire. Lillustrates the injection period when the inlet 30 is open. The pressureF increases until the inlet 30 is opened and then it gradually decreasesas the compressed air in the accumulator 34 exits the inlet 30 into thecylinder. After the inlet 30 is closed and the aperture 38 is opened,the pressure F returns to about the same pressure E as the crankcase 18.One of the features of the present invention is that the inlet aperture30 can be sized to prevent the accumulator 34 from totally discharginginto the cylinder 12. In other words, the accumulator 34 can bepressurized for the entire time that the inlet 30 is open such thatcompressed air is continually exerting pressure out the inlet 30 whenthe inlet 30 is open. This occurs regardless of whether there has beencombustion or a misfire. Since the piston head 40 opens and closes allof the ports/channels 24, 28, 30, 38, 42, the engine 10 can be designedto provide different performance characteristics by changing thepositions of the ports/channels 24, 28, 30, 38, 42 relative along thelength of the cylinder and/or relative to each other along the length ofthe cylinder. This can change the timing of how long the accumulator ischarged with compressed air from the crankcase, how long the accumulatorblows off, how long the accumulator injects into the cylinder, etc. Thiscan also change pressure rate changes, such as if the transfer channel,exhaust outlet or air inlet open sooner or later in the piston cycle.

Features of the above-described embodiment of the present invention havebeen tested on a 25 cc engine having a 75° angled injector aperturelocated 0.1 inch above the top of the transfer channel 42, a combinedcharge and blow off aperture located 0.05 inch below the bottom of theintake channel, an open air inlet, 1 psi fuel pressure with a singlediaphragm fuel pump. For an average low speed of 2430 rpm, the engineproduced the following:

FUEL CORRECTED HC FID HC (g/hr) POWER (KW) (ppm) (g/hr) 64.466 028410.03 26.81

Where HC is hydrocarbon emission; and HC FID is total hydrocarbonemission in C₁H_(1.85) equivalent as measured by a flame ionizationdetector. For an average high speed of 7487 rpm, the engine produced thefollowing:

FUEL CORRECTED HC FID HC (g/hr) POWER (KW) (ppm) (g/hr) 332.448 0.7288438.31 26.97

This resulted in a total HC emission of 31.59 g/bhp*hr (grams/brakehorse power*hour), total CO emissions of 77.25 g/bhp*hr (grams/brakehorse power*hour), and total NO_(x) emissions of 1.41 g/bhp*hr(grams/brake horse power*hour). For the average high speed (wide openthrottle) average HC emission was 28.38 g/bhp*hr; average FC was 0.731lb/hr; and average BSFC was 0.769 lb/bhp*hr, where FC is fuelconsumption and BSFC is brake specific fuel consumption.

Another test of the same engine, but at a rich fuel setting was alsoconducted. For an average low speed of 3513 rpm, the engine produced thefollowing:

FUEL CORRECTED HC FID HC (g/hr) POWER (KW) (ppm) (g/hr) 79.534 037947.69 34.46

For an average high speed of 7496 rpm, the engine provided thefollowing:

FUEL CORRECTED HC FID HC (g/hr) POWER (KW) (ppm) (g/hr) 391.192 0.80013146.97 42.05

This resulted in a total HC emission of 44.18 g/bhp*hr. In addition,total CO emission was 198.1 g/bhp*hr and total NO_(x) emission was 1.098g/bhp*hr. In a lean setting a total emission of 28.69 g/bhp*hr wasobtained.

Additional test numbers were taken as follows:

Engine Speed Fuel Observed Intake SPGT CO CO2 O2 NOx HC RPM lb/hr hpdeg. F. deg. F. % % % ppm ppm 7460 0.609 0.74 88 441 0.44 8.48 9.00 99.98581.9 7478 0.668 0.85 90 457 1.02 9.30 7.51 133.9 8263.4 7494 0.6990.89 93 469 1.54 9.42 6.91 140.8 8796.4 7495 0.722 0.90 93 475 1.94 9.406.60 144.5 10426.8 7503 0.753 0.93 95 477 2.53 9.15 6.43 136.9 11374.27511 0.795 0.98 100 475 3.16 8.91 6.28 132.1 12067.9 7512 0.817 0.98 108475 3.61 8.69 6.17 118.7 13004.9

Referring now to FIG. 7, a graph similar to FIG. 2 is shown of when thetwo accumulator apertures are opened and closed for an alternateembodiment of the engine. In this embodiment of the engine thecompressed air and fuel injection aperture is farther away from the topof the cylinder than shown in FIG. 1A. Thus, the compressed air and fuelinjection aperture opens and closes at areas A′ and A″ closer to the BDCposition of the piston head. The transfer channel is opened at TO beforethe injection port is opened at A′ and the transfer channel is closed atTC after the injection port is closed at A″. This provides an injectionperiod L′ as shown in FIG. 6. With the present invention both closures Aand B can be selected merely based upon location of their respectiveapertures along the length of the cylinder. However, in alternateembodiments, alternative or additional means could be used to openand/or close the two accumulator ports.

Referring now to FIG. 8, an alternative embodiment of a lubricationsystem for the engine is shown. In this embodiment the piston head 62has a hole 64 through its side wall into its interior. The hole 64 isalignable with the inlet aperture 30 such that fuel (with its lubricant)can pass from the aperture 30, through the hole 64, and into theinterior of the piston head 62. The piston head 62 is connected to apiston rod 66 by a bearing 68. The lubricant passing into the interiorof the piston head 62 can also directly lubricate the bearing betweenthe crankshaft and the piston rod 66. Although this type of lubricationsystem will increase hydrocarbon emissions, the increase is very smalland, therefore, still allows the engine to pass upcoming newgovernmental hydrocarbon emission standards.

Referring now to FIG. 9 the engine is shown with an alternate embodimentof the accumulator conduit 70. As noted above, the accumulator functionsas both a compressed air accumulator and as a tuned reflection pipe. Inthis embodiment the accumulator conduit 70 has an expansion chambersection 72 which is adapted to enlarge the length of the reflectedcompression wave relative to the length of the initial compression wave.Thus, the reflected compression wave is spread out over a longer periodof time for a second pressure spike which is longer in time than F₂shown in FIG. 3. The accumulator conduit can be configured to provideany suitable tuned pipe enhancement of the original compression wave.

Referring now to FIG. 10 the engine is shown with another alternateembodiment of the accumulator 80. In this embodiment the accumulator 80provides a continually variable length tuned pipe which is continuallyvariable based upon the speed of the engine. The accumulator 80 has arotatable inner pipe member 82, a sliding seal 84, a first pipe section86 between the injection aperture 30 and the inner pipe member 82, and asecond pipe section 88 between the aperture 38 an the inner pipe member82. The inner pipe member 82 is rotatable as indicated by arrow M tovary the effective pipe length between the two apertures 30, 38. Anysuitable means could be provided to rotate the inner pipe member 82based upon the speed of the engine, such as a mechanical connection to athrottle or an electronic control device. In another alternateembodiment a sliding trombone type of variable length accumulatorconduit could be provided.

The system as described above provides numerous new features. The smallsize of the injection aperture 30 allows for a sustained injectionregardless of whether combustion occurred immediately before theinjection cycle. The accumulator is a closed end system during theinjection cycle for reflection purposes. The transfer channel can beopened before introduction of the fuel into the combustion chamber.Pressure in the accumulator is relieved or blown off in every cycle ofthe piston thereby reducing fuel leakage between the piston head and thecylinder wall from the injection port. Vacuum drawing of fuel into theaccumulator proximate the injection inlet 30 can be used to simplify thetype of fuel pump used, such as use of a simple diaphragm fuel pump. Thelength and shape of the accumulator conduit system can take advantage ofthe compression wave to deliver a reflected compression wave forenhanced fuel and compressed air delivery through the injection inlet30. The reflected compression wave can atomize fuel in the inlet 30,push the injection through the inlet 30 faster, and also atomize fuelagainst substantially static air all ready in the combustion chamber.Thus, there is provided an accelerated late delivery of a portion of thefuel charge which is inherent to the present system. This late deliveryreduces the amount and likelihood of unburned fuel short circuitingdirectly to the exhaust 28. Thus, hydrocarbon emissions are reduced. Thereflected compression wave can be delivered to the injection aperture atthe end of scavenging after BDC. The accumulator conduit has twovariably open and closed ends to provide a closed end tuned pipefunction as well as a compressed air accumulator function and anaccumulator blow off pressure relieve function. Because of the openingand closing natures of the apertures 30, 38, no direct open path isprovided between the cylinder and the crankcase by the accumulator. Thetuned pipe feature of the accumulator conduit can be tuned, such as withan expansion chamber, to spread out the reflected compression wave tocompensate for varying speeds of the engine. Fuel trapping is enhancedto about 80%-95%. Thus, fuel trapping losses can be as low as only 5%.In old style systems fuel trapping was only about 60%-70%. The presentsystem has better fuel efficiency because of reduced combustion loss andreduces occurrences of misfires because of better fuel mixing from thereflected compression wave. The present invention can also be used as aself governing effect to prevent overspeed of an engine, such as in achain saw, because the tuned pipe feature of the accumulator conduit cango out of tune at overly high speeds, thus losing the appropriate timeddelivery of the fuel ramming feature of the reflected compression wave.

It should be understood that the foregoing description is onlyillustrative of the invention. Various alternatives and modificationscan be devised by those skilled in the art without departing from theinvention. Accordingly, the present invention is intended to embrace allsuch alternatives, modifications and variances which fall within thescope of the appended claims.

What is claimed is:
 1. In an internal combustion engine having acrankcase, a cylinder connected to the crankcase, a compressed airassisted fuel injection system connected between the crankcase and thecylinder, and a reciprocating piston head located in the cylinder,wherein the improvement comprises: the compressed air assisted fuelinjection system having a conduit system with a first aperture into thecylinder forming a fuel and compressed air injection port and a secondaperture which, based upon position of the piston in the cylinder, isconnectable to pressure inside the crankcase, the second apertureforming a compressed air entrance and blow off port, wherein the pistonhead opens and closes the two ports as the piston head reciprocates inthe cylinder, wherein the first and second apertures are spaced relativeto each other and the piston head is sized and shaped such that thepiston head substantially simultaneously opens the compressed airentrance and blow off port and closes the fuel and compressed airinjection port, and wherein the blow off port remains open as the pistonhead moves to and through a top dead center position.
 2. An engine as inclaim 1 wherein the injection port is sized to restrict flow of airthrough the injection port such that an entire amount of air exiting theinjection port in a single injection cycle is pressurized and compressedair is left in the conduit system after the injection port is closed. 3.An engine as in claim 1 further comprising a hole in the piston headwhich is alignable with the injection port to allow a lubricant in thefuel to pass from the injection port and into the hole to lubricate abearing connecting the piston head to a piston rod.
 4. An engine as inclaim 1 wherein the cylinder includes a lubrication channel along aninside wall from the injection port to a location past a rear end of thepiston head when the piston head is at the top dead center position. 5.An engine as in claim 4 wherein the lubrication channel opens into anair inlet.
 6. An engine as in claim 1 wherein access between thecylinder and the conduit system is closed and access between thecrankcase and conduit system is open during vacuum pressure in thecrankcase such that fuel is vacuum pulled into the conduit system duringa forward stroke of the piston head toward the top dead center positionand air is compressed into the conduit system during a rearward strokeof the piston head.
 7. An engine as in claim 1 wherein the conduitsystem forms a tuned reflection pipe for the injection port, the conduitsystem having a tuned pipe length to deliver a reflection of acombustion generated compression wave back to the injection port duringa later half of delivery of fuel from the injection port into thecylinder.
 8. In an internal combustion engine having a compressed airassisted fuel injection system connected between a source of compressedair and a cylinder of the engine, wherein the improvement comprises: thecompressed air assisted fuel injection system having a compressed airaccumulator and means for relieving compressed air pressure in theaccumulator during a majority of when a fuel and compressed airinjection port of the injection system is closed by a piston head of theengine and the piston head is moving towards a top dead center position.9. An engine as in claim 8 wherein the means for relieving comprises acombined compressed air entrance and blow off port between theaccumulator and a crankcase of the engine.
 10. An engine as in claim 9wherein the combined compressed air entrance and blow off port isprovided at a bottom of the cylinder.
 11. An engine as in claim 10wherein the piston head opens and closes the combined compressed airentrance and blow off port.
 12. An engine as in claim 11 wherein the twoports are reciprocatingly opened and closed by the piston head.
 13. Anengine as in claim 8 wherein the injection port is sized to restrictflow of air from the accumulator through the injection port such that anentire amount of air exiting the injection port is pressurized andcompressed air is left in the conduit system after the injection port isclosed.
 14. An engine as in claim 8 further comprising a hole in thepiston head which is alignable with the injection port to allow alubricant in fuel to pass from the injection port and into the hole tolubricate a bearing connecting the piston head to a piston rod.
 15. Anengine as in claim 8 wherein the cylinder includes a lubrication channelalong an inside wall from the injection port to a location past a rearend of the piston head when the piston head is at the top dead centerposition.
 16. An engine as in claim 15 wherein the lubrication channelopens into an air inlet.
 17. An engine as in claim 8 wherein accessbetween the cylinder and the accumulator is closed and access betweenthe crankcase and the accumulator is open during vacuum pressure in thecrankcase, and a fuel metering device has an exit connected to theaccumulator such that fuel is vacuum pulled into the accumulator duringmovement of the piston head towards the top dead center position and airis compressed into the accumulator during a movement of the piston headaway from the top dead center position.
 18. An engine as in claim 8wherein the accumulator forms a tuned reflection pipe for the injectionport with a tuned pipe length to deliver a reflection of a combustiongenerated compression wave back to the injection port during a laterhalf of delivery of fuel and air through the injection port into thecylinder.
 19. In an internal combustion engine having a compressed airassisted fuel injection system connected between a source of compressedair and a cylinder of the engine, wherein the improvement comprises: thecompressed air assisted fuel injection system including an accumulatorfor providing a charge of compressed air and an aperture from theaccumulator into the cylinder, wherein the aperture is sized to restrictflow of the charge into the cylinder such that the entire charge duringan injection period as the charge leaves the aperture is pressurized,and a second aperture from the accumulator into the cylinder which isopened behind a piston head of the engine as the piston head movestowards a top dead center position.
 20. An engine as in claim 19 whereinthe means to relieve comprises a second aperture from the accumulatorinto the cylinder which is opened behind a piston head of the engine asthe piston head moves towards a top dead center position.
 21. An engineas in claim 19 further comprising a hole in a piston head which isalignable with the injection port to allow a lubricant in fuel to passfrom the injection port and into the hole to lubricate a bearingconnecting the piston head to a piston rod.
 22. An engine as in claim 19wherein the cylinder includes a lubrication channel along an inside wallfrom the injection port to a location past a rear end of the piston headwhen the piston head is at a top dead center position.
 23. An engine asin claim 22 wherein the lubrication channel opens into an air inlet intothe crankcase.
 24. An engine as in claim 19 wherein the accumulatorforms a tuned reflection pipe for the injection port with a tuned pipelength to deliver a reflection of a combustion generated compressionwave back to the injection port during a later half of delivery of fueland air from the injection port into the cylinder.
 25. In an internalcombustion engine having a compressed air assisted fuel injection systemconnected between a source of compressed air and a cylinder of theengine, wherein the improvement comprises: the compressed air assistedfuel injection system having a conduit between the source of compressedair and the cylinder, the conduit having a first aperture into thecylinder and a second aperture, and the engine has a system for openingand closing the first and second apertures, wherein the second apertureis closed while the first aperture is open, and wherein, as a piston inthe cylinder moves towards a top dead center position, the secondaperture is open during a majority of when the first aperture is closed.26. An engine as in claim 25 wherein both the first and second aperturesextend into the cylinder and the piston head reciprocally opens andcloses the apertures.
 27. An engine as in claim 25 wherein the secondaperture is connected to pressure in a crankcase of the engine when thesecond aperture is open.
 28. An engine as in claim 25 wherein theconduit has a length and the second aperture is closed to form a tunedreflection pipe for the first aperture to receive a compression wavefrom combustion in the cylinder and reflect the compression wave back tothe first aperture during a later half of the first aperture being open.29. An engine as in claim 27 wherein the conduit includes an expansionchamber section to lengthen the reflected compression wave.
 30. Anengine as in claim 25 wherein the first aperture is sized to restrictflow of air through the injection port such that compressed air is leftin the conduit after the first aperture is closed.
 31. An engine as inclaim 30 wherein the second aperture is connectable to pressure in acrankcase of the engine such that pressure from the compressed air inthe conduit after the first aperture is closed is relieved into thecrankcase.
 32. In an internal combustion engine having a compressed airassisted fuel injection system connected between a crankcase and acylinder of the engine, wherein the improvement comprises: thecompressed air assisted fuel injection system having a conduit betweenthe crankcase and the cylinder, a fuel metering device with a fuel exitinto the conduit, and wherein a piston head of the engine opens andcloses access to the conduit from the cylinder and the crankcase,wherein access between the cylinder and the conduit is closed and accessbetween the crankcase and conduit is open during vacuum pressure in thecrankcase such that fuel is vacuum pulled into the conduit during aforward stroke of the piston head and air is compressed into the conduitduring a rearward stroke of the piston head.
 33. A method of injectingair and fuel into a cylinder of an internal combustion engine comprisingsteps of: compressing air into an accumulator; opening an injection portinto the cylinder and injecting the compressed air from the accumulatorand fuel from the injection port into the cylinder; closing theinjection port; and opening a blow off port of the accumulator torelieve residual compressed air pressure from the accumulator.
 34. Amethod as in claim 33 wherein the step of compressing air comprisesopening the blow off port and allowing compressed air to enter theaccumulator through the blow off port.
 35. A method as in claim 33wherein the steps of opening and closing comprise moving a piston headof the engine over and away from the ports.
 36. A method as in claim 33further comprising passing lubricant from the injection port into a holein a piston head of the engine to lubricate a bearing between the pistonhead and a piston rod.
 37. A method as in claim 33 further comprisingpassing lubricant from the injection port along a channel on an insidesurface of the cylinder to a location past a rear end of a piston headof the engine.
 38. A method as in claim 33 further comprising closingthe blow off port when the injection port is opened to form theaccumulator into a closed end tuned reflection pipe.
 39. In an internalcombustion engine having a compressed air assisted fuel injection systemconnected between a source of compressed air and a cylinder of theengine, wherein the improvement comprises: the compressed air assistedfuel injection system having a compressed air accumulator and a reliefsystem for relieving compressed air pressure in the accumulator during amajority of when a fuel and compressed air injection port of theinjection system is closed by a piston head of the engine and the pistonhead is moving towards a top dead center position, wherein the reliefsystem comprises a combined compressed air entrance and blow off portbetween the accumulator and a crankcase of the engine, and wherein thecombined compressed air entrance and blow off port is provided at abottom of the cylinder.
 40. In an internal combustion engine having acompressed air assisted fuel injection system connected between a sourceof compressed air and a cylinder of the engine, wherein the improvementcomprises: the compressed air assisted fuel injection system having aconduit between a first aperture into the cylinder and a second aperturerelatively lower of the cylinder, and the engine has a piston whichdirectly opens and closes the first and second apertures, wherein thesecond aperture is closed by the piston during a majority of when thefirst aperture is open, and wherein the second aperture is open during amajority of when the first aperture is closed by the piston.
 41. In aninternal combustion engine having a crankcase, a cylinder connected tothe crankcase, a compressed air assisted fuel injection system connectedbetween the crankcase and the cylinder, and a reciprocating piston headlocated in the cylinder, wherein the improvement comprises: thecompressed air assisted fuel injection system having a conduit systemwith a first aperture into the cylinder forming a fuel and compressedair injection port and a second aperture communicating with thecrankcase and forming a compressed air entrance, wherein the piston headopens and closes the two ports as the piston head reciprocates in thecylinder, and wherein the cylinder includes a lubrication channel alongan inside wall from the injection port to at least partially define apath to a location past a rear end of the piston head when the pistonhead is at a top dead center position.
 42. In an internal combustionengine having a compressed air assisted fuel injection system connectedbetween a source of compressed air and a cylinder of the engine, whereinthe improvement comprises: the compressed air assisted fuel injectionsystem including an accumulator for providing a charge of compressed airand an aperture from the accumulator into the cylinder, wherein theaperture is sized to restrict flow of the charge into the cylinder suchthat the entire charge during an injection period as the charge leavesthe aperture into a combustion chamber of the cylinder is pressurized,and wherein the cylinder includes a lubrication channel along an insidewall from the injection port to at least partially form a lubricantdelivery path from the injection port to a location behind a rear end ofthe piston head when the piston head is at a top dead center position.43. A method of injecting air and fuel into a cylinder of an internalcombustion engine comprising steps of: opening an injection port intothe cylinder and injecting the air and fuel from the injection port intothe cylinder; closing the injection port; and passing lubricant from theinjection port along a channel on an inside surface of the cylinder to alocation behind a rear end of a piston head of the engine.
 44. A methodas in claim 43 further comprising compressing the air into anaccumulator and injecting the compressed air with the fuel from theinjection port.
 45. A method as in claim 44 further comprising opening ablow off port of the accumulator to relieve residual compressed airpressure from the accumulator.
 46. A method of lubricating a two strokeengine comprising steps of: transporting a first fuel and oil mixturequantity with air into a combustion chamber of a cylinder of the engine;and transporting a second fuel and oil mixture quantity with air into acrankcase of the engine; wherein the first mixture quantity istransported into the combustion chamber without passing through thecrankcase, and wherein the second mixture quantity is not a sufficientquantity for operation of the engine without the first mixture quantitybeing transported into the combustion chamber.
 47. A method as in claim46 wherein the first and second fuel and oil mixtures are provided asbeing substantially identical.
 48. A method as in claim 47 wherein thefirst and second fuel and oil mixture quantities are supplied from acommon premixed supply.
 49. A two stroke engine comprising: a crankcase;a cylinder connected to the crankcase; a piston located in the cylinder;and a dual intake system for supplying air, fuel and lubricant, whereina first intake of the dual intake system supplies a first quantity of afuel and lubricant mixture for injection with air directly into acombustion chamber in the cylinder, and wherein a second intake of thedual intake system supplies air and a second quantity of the fuel andlubricant mixture to the crankcase, wherein the second quantity issubstantially smaller than the first quantity.
 50. A two stroke enginecomprising: a crankcase; a cylinder connected to the crankcase; a pistonlocated in the cylinder; and a system for supplying air, fuel andlubricant, the system comprising: a first intake for supplying a richair, fuel and lubricant mixture for injection directly into a combustionchamber of the cylinder, a second intake for supplying air to thecrankcase, and a path between the first intake and the crankcase fortransporting a portion of the rich mixture from the first intake forintroduction into the crankcase for providing lubrication in thecrankcase.
 51. An engine as in claim 50 wherein the path extends fromthe first intake into the second intake and then into the crankcase. 52.An engine as in claim 50 wherein the path is located to be selectivelyopened and closed by the piston.
 53. An engine as in claim 50 whereinthe path includes a slot along an interior side of the cylinder.
 54. Amethod for providing air, fuel and lubricant in a two stroke enginecomprising steps of: providing a rich air, fuel and lubricant mixturethrough a first intake for injection directly into a combustion chamberof a cylinder of the engine; providing air through a second intake intoa crankcase of the engine; diverting a relatively small portion of therich mixture passing through the first intake from the first intake intothe crankcase for providing lubrication in the crankcase.
 55. A methodas in claim 54 wherein the step of diverting comprises passing theportion along a slot in an inner surface of the cylinder.
 56. A methodas in claim 55 wherein the step of diverting comprises passing theportion from the slot into the second intake.
 57. An engine as in claim32 wherein access to the conduit from the cylinder comprises aninjection port located above a top surface of the piston head when thepiston head is in a bottom dead center position.